Calculating machine



Dec. l, 1942. G, H. HELLGREN 2,303,692

CALCULATING MACHINE Filed Aug. 16, 1938 5 Sheets-Sheet 2 IIJ 169 16.6, I u JWI.

3./9 de M De 1 1942- G. H. HELLGREN 2,303,692

CALCULTING MACHINE Filed Aug. 16, 1938 5 Sheets-Sheet C5 Dec. 1, 1942. G. H. HELLGREN CALCULATING MACHINE Filed Aug. 16, 1958 5 Sheets-Sheet 4 S wmf Patented Dec. 1, 1942 CALCULATING MACHINE Gustaf Hilarius Hellgren, Malarhojden, Sweden Application Augustl, 1938, Serial No. 225,222 In Sweden August 21, 1937 Claims.

This invention relates to improvements in calculating machines of the type in which diierential members such as rods, racks, toothed segments or similar reciprocating or swinging members are displaced so as to cooperate or be stopped` by a set key or similar stop member which corresponds to the amount involved in the calculation operation. The invention is particularly concerned with a novel construction that will enable new items involved in the next following calculation operation to be set up in the machine before the preceding operating cycle of the machine has been completed.

lt is the primary object of the invention to provide a calculating machine which may be operated with greater working speed than machines of the same type hitherto known, and with as little strain and wear as possible on the moving parts.

Another object of the invention is to provide a novel construction'which enables the use of a weaker spring for the handle of manually operated calculating machines.

More specically stated the object is to provide a machine having adjustable stop pins mounted on a carriage and differential members adapted to cooperate with said stop pins, the arrangement being such that the stop pins and the said members are moved away from each other at the end of the forward stroke or immediately at the beginning of the return stroke of the main shaft in order to enable the differential members to freely most past such stop pins which may a1- ready have been set for the next following calculation operation. In machines hitherto known, as long as some of the set members or those which during the calculation operation proper cooperate with each other do not occupy initial position, it is not possible to prepare the next following calculation operation, that is to say to set up the new figure involved, because the parts concerned would prevent the movement to initial position of those parts which have been set or adjusted at the preceding operation.

In accordance with the present invention the differential members, for instance, in the form oi rods, racks, toothed segments or the like cooperating with pins, keys, or the like stop means, are mounted for the said purpose on a supporting member which is movable in such manner that the said differential members, having the supporting member in a certain position, can freely move pas; said stop pins or the like (that is to say they will not cooperate with said stop pins or the like). For this purpose the differential members are mounted on a frame which may be rocked or turned or displaced parallel with itself in the same or opposite direction in which the stop means are set and which is so connected with the driving member of the calculating machine that the differential members are brought out of the path of movement of the stop pins or the like immediately upon the differential members having occupied the desired set position. The differential `members are preferably provided with or adapted to cooperate with locking means in order to retain the same in their set position even after they have been brought out of engagement with the stop pins or the like.

The invention may be applied to calculating machines of the types described above. It is especially suitable for manually driven machines carrying out additions and of the ten key type, but naturally it may also be applied to multiple key adding machines.

Other objects and advantages will appear from the following specification and drawings.

The invention as applied to different types of key boards is illustrated in the accompanying drawings in which- Figure 1 is a front elevation, partly in section, of the key board portion of a machine embodying the invention, the casing and the front plate of the machine frame having been removed to expose the interior mechanism, the keys l and 9 l of the ten key type embodying the invention, the

casing being broken away and some plates of the machine frame being removed to expose the interior parts. The keys representing zero and the amounts 1, 5 and 9 only have been shown.

Fig. 4a is a fragmentary side elevation, as seen from the left side, of the totalizer and the subtract key control elements, the tens transfer device being omitted for clearness.

Fig. 5 is a partial view similar to Fig. 4 except that the frame with the differential members is shown in working position.

Fig. 6 is a plan View of the details shown in Fig. 4.

Fig. 7 is a perspective view of the movable frame supporting the differential members, a few of which only are shown for the sake of clearness.

Fig. 8 is a diagrammatic view in right side elevation of a portion of a multiple key board machine to which the invention has been applied.

Fig. 9 is a partial plan view of a portion of the key board shown in Fig. 8.

Fig. 10 is a lateral view of one of the keys of Fig. 9 in three different positions.

Fig. 11 is a diagrammatic view in right side elevation of a portion of another type of multiple key board machine to which the invention has been applied.

Like parts are identified by the same reference numbers throughout the several views, modifications having the aflix a, b and so on.

The totalizer may be provided with a tens carrying mechanism of the type as shown and described in my Patent No. 2,008,355. For the sake of clearness and as not constituting a part of the present invention, such-tens carrying mechanism, however, has not been described or illustrated in the drawings. It is further possible to provide a machine containing the present invention with a printing device of conventional type.

General constructfm 'Ihe machine illustrated in Figs. 1-6 is provided with a set of ten adjustable amount keys, while the modifications shown in Figs. 8 and l1 belong to machines which are provided with a plurality of banks of adjustable amount keys.

The machine as shown in Figs. 1-6 is provided with a main drive shaft II which, during the machine operation, is first rocked counterclockwise as viewed in Fig. 4 and then returned clockwise. This shaft may be operated by a hand lever or by a motor. The machine illustrated is a manually driven machine, the hand lever I2 being keyed to the shaft II.

The amount keys I and the key 2 are adapted to actuate stop pins mounted on a carriage I3, which pins, when the machine is operated, control the longitudinal movement of differential members I4 pivoted to actuator racks I5.

The chief feature of the invention is the mounting of the differential members I 4 on a movable frame I6, I6a which is connected to the same mechanism which controls the engagement and disengagement of the actuator racks I with the totalizer I'I, which latter is of the so called "tumbling frame type.

The structure of the various sub-mechanisms Will now be described in detail.

The driving mechanism To the shaft II is keyed an arm 2I connected to one end of a link 22 (Fig. 4) whose other end is connected to av double-armed lever 23, 24 pivoted about a shaft 25 which is journalled in a suitable manner such as indicated by the bracket 26 fixed to the bottom plate 3 of the casing.-

the return stroke of the handle I2 is limited, '"5" while the forward stroke is limited by a finger 34 integral with the arm 2| and a stud 35 attached to a bracket 36 which supports the main drive shaft II. This latter is adapted to be rocked about in forward direction and thus also 110 when it is returned.

The upper arm 23 has attached thereto two rollers 31, 38 adapted alternately to engage a notch 39 .in the lower edge of a link 40, a spring 4I tending to keep either of the rollers in engagement with the notch 39. The rearward end of the link 40 is pivoted as at 42 to the upper end of an arm 43 the lower end of which is pivoted to a stud 44 attached to the bracket- 28. The forward end of said link 40 has a slot 45 engaging a stud 46 attached to one of the frame plates 41, 48 which support the totalizer I1. The link has a projection 49 adapted to be brought periodically behind a stop 50 xed to the machine frame.

The stud 42 further supports one end of a rod 5I bent at several places and pivoted at its forward end to a link 52 which is connected to the upper arm 53 of a bell-crank 53, 54 which is pivoted about a stud 55 attached to the machine frame. The lower or forward arm 54 of the bell-crank has a notch 56 engaging a pin 5l fixed to one or two bars I6, I6a pertaining to the frame which supports the differential members I4.

The sector 3I is connected by means of a link 58 to a three-armed lever 59, 60, 6I keyed to a shaft 260 supported by the machine frame and itself supporting the actuator racks I5. At the left side of the machine, as seen in Fig. 6, a similar lever is keyed to the shaft 260, and the arms 60 and 6I of the levers by a rod 62 and by a rod 53, respectively. Each rack I5 is connected with the spindle 62 by means of a spring 64 which in initial position of the parts, such as shown in Fig. 4, is not or only slightly tensioned. All racks normally rest against the rod 63 and the movement of the racks in clockwise direction is limited by a stop 65 attached to the machine frame. The said springs 64 will be tensioned when, during the forward stroke of the handle I2, the lever 60 is turned counterclockwise, so that the springs tend to also turn the racks in the same direction to an extent which is determined by the differential movement 0f the members I4. These members I4 are pivoted to their individual racks I5 by means of studs 66.

Supporting frame for differential members The differential members I4 are slidably mounted, according to the present invention, with their bent forward ends 6l on wires 68 which are secured to the forward plate 69 of the frame I6, 69, ISa (Figs. 2 and 4), on one end, and to a. transverse plate l0 of said frame, on the other end. The rearward end of the two side plates I6, IBa are pivoted on a shaft II which is journallcd in brackets l2, 13. Each differential member I4 has a shoulder 'I4 extending downwardly and adapted to cooperate either with the 0 rail I5 that is fixed to the plate 83, Fig. 1, or with one 0f the stop pins I6 on the carriage, which has been set by a numeral key as will be described later. The upper edge of each differential member has a series of ten teeth 1l adapted to cooperate with a pawl 'I8, when the frame I6, 69, Ilia is in its upper position, such as illustrated in Fig. 4. The pawls 'I8 are pivoted on a spindle I9 mounted on the side plates I 6, I 5a. Toward the differential ying the pawls against said shaft.

member each pawl has an inclined surface 80 cooperating with a fixed shaft 8|, springs 82 urg- When the frame I6, 69, I 6a is rocked counterclockwise, as will be explained later, the pawls 18 slide with the inclined surfaces around the fixed shaft 8|-, so that they leave their engagement with the teeth 11 and the differential members I4 are allowed to be moved toward the rear end of the machine. At the rocking of the frame I6, |59, IBa in opposite direction, that is clockwise, the springs 82 will draw the pawls 18 into engagement with that tooth 11 of the differentiaI member |4 which lies in register with the pawl and which is determined by the diiferential movement of the member I4 at the calculation operation under conside eration.

The carriage 16 of substantially rectangular rail are mounted for axial The stop pins section and the (Figs. The sleeves 85, B1 are mounted for free displacement on a shaft 94 xed to two side plates 95, 96 of the machine frame. upper plate 83 and the lower plate 9| are provided with rows of ten holes each, through which holes extend the stop pins representing the numerical values 0, 1, 2 and so on, to 9 inclusive, in each row. The 0 rail 15`is arranged in the same line as the 0 stop pins 16, that is the pins in the rst (lowest) line (Fig. 2). carriage is in normal position (to the right, Figs, l and 2) the 0 rail 15 prevents all differential members I4 from moving rearwardly. According as the carriage moves step by step to the left, when the machine is operated, the diiferential members |4 will be free one after the other, counted from the right (Fig. l), and may now move rearwardly until stopped by the pins 1B which have been set: Each pin 16 is pressed in between its ends to form a projection 91 of somewhat triangular section, and individual leaf springs 98 of corresponding shape are inserted between two adjacent pins serving to retain the pertaining pin in either of the two positions,

can cooperate with the shoulders 14 on the differential members I4 and a lower ineffective or normal position such as shown in Fig. 4. lower carriage plate 9| hasa means of a link IUI. The said arm |00 belongs to a driving device for the carriage as will be described later.

The carriage driving device The arm |00 is integral with a pivoted lever is urged by a spring |04 to turn greater than that required to restore the carriage to normal position, During the early part of the forward stroke of shaft 25, during which the shaft of the member 200 and at the same time moves the rod IIO and all parts connected thereto to the left, see also Fig. 13. When thereafter the operator releases the handle, the main spring 21, Figs.

handle I2 and thus the shaft 25 must, however, move further, that is to say the pin II2 moves from the radius .1r-x to the position shown in Fig. 14. During this extended stroke the pin carriage is pushed slightly beyond its normal forward position, and the stud |06 then engages the tip |09 of the finge |01 to shift the finger |01 to the right, Fig. 2, .-.nd out of engagement with the roller |05. All of the previously actuated mal position `by the spring |04 when the finger |01 leaves the roller |05. Since the carriage is restored to normal position before the shaft 25 and main shaft II complete their return strokes,

out awaiting the completion of the previous value in the totalizer.

The key board It is to be observed that only the bell-cranks pertaining to the keys 0, 1-8, such hammer-like projection, while the 9 bell-crank terminates at H8, because the 9 pins are utilized to con- Iil which supports the a plate |20 having a bell-cranks IIS is pivot-ed ridge |2| extending over all levers IIB, a spring |22 urging the plate |20 against the latter. A hammer-like projection |23 is formed on the plate |20 and is situated immediately below the pin T6 representing the value 9" (Figs. l and 2). As the carriage proceeds step by stepy to the left, the pins 9 'rest with their lower ends |24 against a stop |25 fixed to the bottom plate 3. The device just described Works in a manncr'similar to the esrapement of a tvpe-writer machine. When a key I is pressed down, the hammer I|`| presses the pin 13 upsame row upwardly, so

is freed from the stop and the spring |04 draws the carriage to the left about half a step, inasmuch as the 9 pin of the next following row will abut the right hand surface of the projection |23. When, now, the key is released, a spring |26 urging the same back to normal, the projection |23 leaves the said 9" pin which now, by the action of the spring |04, will be pressed against the stop |25, the carriage having thereby completed the second half step to the left.

The key board may of course be completed with control keys of the usual type and for conventional purposes. Of these keys only that one has been shown which is adapted to tumble the totalizer over to subtract position.

The totalieer As stated above the totalizer is in this particular case of the tumbling frame type. The side plates 41, 48 of the totalizer rocking frame are mounted for oscillation on the main shaft Each plate has a stud |30 on which is pivoted a frame |3| supporting two spindles |32, |33. The spindle |32 supports the so called add wheels |34 each provided with a numeral drum |35, the figures of which may be read through a window 4 arranged in the casing 5 of the machine. Normally the wheels |34 are in mesh with the teeth |36 of the actuator racks |5 and they are permanently in mesh with the so called subtract wheels |31 mounted on the spindle |33. Immediately at the beginning of the forward stroke of the shaft the totalizer |1 is rocked away from the racks, so that these latter may be differentially positioned in accordance with the settings of the pins 16. At the end of the forward stroke the frame |3| may be tumbled, if desired, to subtract position, or vice versa to add position. Immediately at the beginning of the return stroke of the shaft the totalizer, either with its add wheels |34 or with its subtract wheels |31, is brought into mesh with the actuator racks I5, so that the movement of the latter back to normal may be transmitted to the totalizer, whereby the amount set up by the keys 2 is registered in the totalizer.

The subtract key The arrangement -for changing the totalizer over from add position to subtract position by means of the subtract key may be of any conventional type. A suitable form thereof has been illustrated in Fig. 4 and consists of the following parts.

The subtract key |40 has a stem |4I with a notch |42 adapted to snap beneath a stop |43 fixed to the casing 5, when the key is pushed down and pressed slightly backwardly, a spring |44 tending to hold the key in this depressed position. To again release the key it will only be necessary to draw with the finger the key somewhat forwardly and to remove the finger, so that the spring |44 draws the key upwards. A pivoted lever |45 has an open slot |46 engaging a stud |41 on the key stem |4|, the other end of the lever being connected to the minor tumbling frame |3| supporting the totalizer wheels, by means of a spring |48 normally extending below the axis of rotation |30 of said totalizer frame. This frame |3| has two radial projections |49, |50, one |49 serving to limit the tumbling movements of the frame |3| against two stop pins |56, |51, the other |50 being wedge-shaped with opposed surfaces |50a, |50b adapted to cooperate alternately with a stud |5| on a pivoted doublearmed lever |52, 253, see Fig. 5. A spring |54 urges the lever counterclockwise, Fig. 5, to press the stud |5| towards the frame |3| and into engagement with one of the surfaces |50a, |50b of projection |50, and the lever may be rocked in the opposite direction by a stud |5| which cooprrr erates with the free end of the arm |53, the stud being mounted on an arm |56 that is fixed to the main shaft 25. The subtract key mechanism just described operates in the following manner. The parts of the totalizer mechanism come to rest after an addition in the positions shown in Fig. 4, with the add wheels |34 in engagement with the teeth of the actuator racks l5, since the spring |48 has rocked the totalizer frame |3| clockwise to the limit determined by the engagement of the projection |49 with .the stop |56. The main frame plates 41, 48 rock counterclockwise to m'ove the totalizer frame |3| and the add Wheels |34 away from the actuator racks l5 at the beginning of a cycle of operations, but the angular position of the frame |3| on the main frame plates 41, 48 is not altered when the wheels leave the rack teeth |36 as the spring |48 retains the projection |48 against the upper stop pin |56. However, when the subtract key |40 is depressed, the spring |48 extends from the lever |45 to the tumbling frame |3| above the axis of rotation |30 of the latter, thereby tending to throw the same over into the subtract position. This, however, cannot yet occur, until the totalizer main frame 41, 48 has rocked over to its extreme forward position and not until about at the end of the forward stroke of the handle |2 the stud |55 engages the lever |53, thereby releasing the stud |5| from the shoulder |50a of the minor frame |3|, so that this latter tumbles over to the subtract position. In this position it will remain as long as the key |40 is pressed down. When the main frame 41, 48 is tumbled backwardly into the position shown in Fig. 4 the stud |5| will lie on the shoulder |50b. When the key |40 is released after a subtraction operation, the spring |48 will be positioned as shown in Fig. 4 tending to tumble the frame |3| over tc add position. This, however, cannot occur until at about the end of the subsequent forward stroke of the handle |2 the stud |55 has removed the lever |52, |53 with the stud |5| away from the shoulder |50b, so that the rocking of the frame |3| now can take place.

It thus will be clear, that the tumbling of the minor totalizer frame |3| only occurs when the wheels |34 or |31 are out of engagement with the racks |5.

Mode of operation With all parts at normal, including the subtract key in raised position and the add wheels |34 in mesh with the rack teeth |36, the first number is set up by the keys l, whereby the pins 16 are raised and the carriage is displaced step by step to the left, the roller |05 sliding along the left-hand edge of the finger |01 (Fig. 2). Now, the handle |2 is turned counter-clockwise (Fig. 4), and immediately at the beginning of the forward rocking movement of the shaft the roller 31 pushes the link 40 to the left, thereby rocking away the totalizer |1 from the racks |5 and rocking the bell-crank 53, 54 counterclockwise. In this way the frame |5, 69, |6a is rocked about the shaft 1| and the shoulders or hooks 14 on the differential members or rods |4 are lowered, so that they stand immediately in front of the 0 rail 15 or in front of the first deft-hand, mg. 4) meer the pms u. simultaneously the shaft 26 is rotated counter-clock-l notch 29 of the arm 26 has reached the stud 39 on the segment 3| which now follows the rocking of shaft 26. By meansy of link I6, the lever 69, 6| is turned counter-clockwise, thereby tensioning the springs 64 and removing the rod 63 from the. y racks i6 which will be drawn differentially bythe springs 64 in cour Leer-clockwise direction to such extent as will be determined by the rearward stroke of the rods Il in accordance with the stop pins 16 raised.

At the end of the Iorward stroke of the handle i2 the finger |01 has reached the position shown in Fig.v 3 and it is now prepared to engage vthe roller |06, immaterial of which position the carrlage i3 occupies. in a position which would correspond to the extreme` left position of the carriage. It is clear that an engagement between the linger |01 and the roller |66 always will take place duringthe return stroke of the handle at any position of the carriage between its two extreme end positions.

At the end oi' the forward stroke the roller Il Fig. 13 shows the lever |02, ||l3- '5 Multiple keyboards Y The invention applied to a calculating machine -of the type .employing banks of amount keys, one

bank ior each denomlnational'order, in which no .stop pins supporting carriage is necessary, is illustratedintwo embodiments in Figs. 8-11.

In the first of these two embodiments the hook 14a of 4the differential members Ma cooperate direct with the key |68 which has been set (pressed down). `The keys cooperate with a plate l whch'is pvotally connected to a zero stop |52. Rg. lfshows the key in three positions which disclose that the 'stop .is lifted out 0f the path tf movement of thev diierential member' Ida as soon as a numeral .key is pressed down. The stems |63 of .the keys are bentvin this case in order to render possible a limited movement i oi?A the -diierential member Ila. This may also be ach eved in connection with straight key stems by means 'of a lever system of the kind such as for instance shown in Fig. 1l. lin this case the rod Hb is pivotally connected to adouble-armed lever i 65, |66, the arm |65 of which is considerably ,longer than the arm |66, so that the differential memberv |61 pivotally connected to the latter moves, in accordance with theratio of gearing |66: |65, a shorter distance than the rod Mb. The diiferential member |61 has shoulders |68 adapted to .cooperate in known manner with the pertaining key stern |99. The dinerential member |61 is further provided with a zero 'stop |10 adapted to cooperate with -a bell-crank |1| which is actuated 'by alatching slide |12 has reached a position in which it registers with .thenotch 39, and the link 46 is drawn downwardly by the spring 9|, so that the projection 49 reaches a lower position `than the lower edge 'of the stop 60, thereby rendering the mechanism ready for the return stroke. l v

Immediately at the .beginning of the return stroke the link Il is displaced rearwardly by the action of the roller 39 on the notch 39. Thus,

the totalizer |1 is thrown into gear withv the racks and the i'rame i6, 69, |8a is again raised to the vposition vshown in Fig. 4, which will permit the setting .up ot new figures, i. e., raise the respective pins -18 on thecarriage, as soon as the latter has returned to normal The handle I1 may now be released (by the right hand) and the free Ahand may be utilized to set up the new gure assoon as the carriage Itis returned to initial posiends to two guided vertical rods1l18, |19, the' cooperating with the key stems. The difierential member |61 receivesin the presentoase a vertical movement parallel with itself by means of the following device. The rod |6b which is a modification of the rail I6 according to Fig. 4,

vhas a prolongation |14, at the end of which is iixed a pin |15 extending into a slot |16 of a horizontal rail |11. This` latter is xed at the upper ends oi' which support spindles |99, |I|l which extend into slots |92, A|93 ofthedinerential'members |81. It is to be. observed that a set of the partslb, |14|19 is arranged at each side of the differential members assembly in or tion. The main spring 21 which as a consequence of the new construction, may be made considerably weaker than in machines ofthe same ltime hitherto known, whereby the wear of the moving parts is reduced, draws the lever Il, 26 in clockwise direction, the notch 29 of the arm 26 changing sides ofthe Vstud It, so that the segment-3| is also turned clockwise. When the link v4|) has been displaced to theright by the roller to its end position, Fig. 4, the roller 91 lifts the link,

der to assure avsatisiactory parallel movement. The mode of operation is otherwise of the same kind as that described in connection with Figs. 1-64. l f y What I claim is: 1. In a calculating machine, the-'combination with a totalizer, actuator racks, longitudinally movable diiierential members vconnected to each actuator rack, stopmeans adjustable from normal inoperative positions to. cooperate with said' v which is permitted by the slot 6I at the end of the.

link 49,' audit slides along the lower edge thereof until it finally snaps into the notch I9. l

The-rocking of the sector 3| is accompanied by the rocking of the lever Il, 6| clockwise, whereby the rod '63 pushes all racks which had been displaced under the preceding forward stroke of the machine, back to normal and at the same time e this rotary movement is transmitted to the totalizer i1, the final result being visible through the window I.

diilerential members to limit,..the longitudinal movement thereof in accordance with the value to be entered in seid totauzer. and means includ` ing a cyclically operable lmain shaft for, oper-vl 'ating'said differential members .and actuator racks to enter the value in said totalizer, or a movable' support including means slidably mounting said dmerential members for-longitudinal movement. and means actuated by said main shaft prior to the completion of'an entry into said totalizer by said actuator racks to displace said support to move said differential mem-l bers away from thestop 2. In 'a calculating machine, the combination witha totalizer, actuator racks, a plurality oi axially adjustable stop means, longitudinally movable differential members attachedto said racks and cooperating with said stop means, and a rocking drive shaft, of a support on which said differential members are slidably mounted for longitudinal movement, means mounting said support for movement substantially parallel to the direction of axial movement of said stop means, and means actuated by said drive shaft to move said support towards the said stop means at the very beginning of the forward rocking of the drive shaft and to move the support away from the stop means at the very beginning of the return stroke of the diuve shaft.

3. In a calculating machine, a. totalizer, adjustable stop means, actuator racks, longitudinally movable differential members attached to said racks and limited as to longitudinal movement by said stop means, a rocking drive shaft, a rockable frame slidably supporting said differential members for longitudinal movement, and means actuated by said drive shaft to rock the frame towards the stop means at the very beginning of the forward stroke of the drive shaft and to rock the frame away from said stop means at the very beginning of the return stroke of the drive shaft.

4; In a calculating machine, a totalizer, adjustable stop means, actuator racks, longitudinally movable differential members each pivotal- 1y connected lat one end thereof to individual actuator racks, said differential members being controlled as to longitudinal movement by said stop means, a rocking drive shaft, a rockable frame slidably supporting the other end of each differential member, and means actuated by said drive shaft to rock the frame towards said stop means at the very beginning of the forward stroke of the drive shaft and to rock the frame away from said stop means at the very beginning of the return stroke of the drive shaft.

5. In a calculating machine of the type having adjustable stop means and a totalizer; actuator racks, differential members attached to said racks for cooperation with said stop means, a rocking drive shaft, a rockable frame supporting said differential members, means actuated by said drive shaft to rock said supporting frame towards said stop means to carry said differential members into position to engage the stop means and thereafter to rock said supporting frame Vaway from said stop means, means for moving GUSTAF HILARIUS HELIGREN. v 

